Configurația la rulare

Although the default APC settings are fine for many installations, serious
users should consider tuning the following parameters.

There are two primary decisions to be made configuring APC. First,
how much memory is going to be allocated to APC; and second, whether APC
will check if a file has been modified on every request. The two ini
directives that control these settings are apc.shm_size
and apc.stat, respectively. Read the sections on these
two directive carefully below.

Once the server is running, the apc.php script that
is bundled with the extension should be copied somewhere into the docroot and
viewed with a browser as it provides a detailed analysis of the internal
workings of APC. If GD is enabled in PHP, it will even display some
interesting graphs. The first thing to ensure, of course, is that it is
actually caching files. If APC is working, the Cache full count
number (on the left) will display the number of times the cache
has reached maximum capacity and has had to forcefully clean any entries that
haven't been accessed in the last apc.ttl seconds. This
number is minimized in a well-configured cache. If the cache is constantly
being filled, and thusly forcefully freed, the resulting churning will have
disparaging effects on script performance. The easiest way to minimize this
number is to allocate more memory for APC. Barring that, the apc.filters
ought to be used to cache fewer scripts.

When APC is compiled with mmap support (Memory Mapping), it will use only one
memory segment, unlike when APC is built with SHM (SysV Shared Memory) support
that uses multiple memory segments. MMAP does not have a maximum limit like SHM
does in /proc/sys/kernel/shmmax. In general MMAP support is
recommeded because it will reclaim the memory faster when the webserver is
restarted and all in all reduces memory allocation impact at startup.

apc.enabled can be set to 0 to disable APC. This is
primarily useful when APC is statically compiled
into PHP, since there is no other way to disable
it (when compiled as a DSO, the extension
line in php.ini can just be commented-out).

The number of shared memory segments to allocate
for the compiler cache. If APC is running out of
shared memory but apc.shm_size
is set as high as the system allows, raising
this value might prevent APC from exhausting its memory.

The size of memory to use as a shared buffer for strings used internally
by APC. Size Should be suffixed by M for megabytes, G for gigabytes.
Enabling this option will reduce the amount of memory used per PHP-FPM
worker as strings will be stored once rather than for each worker.

A "hint" about the number of distinct source files
that will be included or requested on your web
server. Set to zero or omit if unsure;
this setting is mainly useful for sites that have
many thousands of source files.

The number of seconds a cache entry is allowed to
idle in a slot in case this cache entry slot is
needed by another entry. Leaving this at zero
means that APC's cache could potentially fill up
with stale entries while newer entries won't be
cached. In the event of a cache running out of
available memory, the cache will be completely
expunged if ttl is equal to 0. Otherwise, if the
ttl is greater than 0, APC will attempt to remove
expired entries.

The number of seconds a cache entry is allowed to
idle in a slot in case this cache entry slot is
needed by another entry. Leaving this at zero
means that APC's cache could potentially fill up
with stale entries while newer entries won't be
cached. In the event of a cache running out of
available memory, the cache will be completely
expunged if ttl is equal to 0. Otherwise, if the
ttl is greater than 0, APC will attempt to remove
expired entries.

The number of seconds that a cache entry may
remain on the garbage-collection list. This value
provides a fail-safe in the event that a server
process dies while executing a cached source file;
if that source file is modified, the memory
allocated for the old version will not be
reclaimed until this TTL reached. Set to zero to
disable this feature.

A comma-separated list of POSIX extended regular
expressions. If any pattern matches the source
filename, the file will not be cached. Note that
the filename used for matching is the one passed
to include/require, not the absolute path. If the
first character of the expression is a + then the
expression will be additive in the sense that any
files matched by the expression will be cached, and
if the first character is a - then anything matched
will not be cached. The - case is the default, so
it can be left off.

If compiled with MMAP support by using --enable-mmap
this is the mktemp-style file_mask to pass to the
mmap module for determining whether your mmap'ed memory
region is going to be file-backed or shared memory
backed. For straight file-backed mmap, set it to
something like /tmp/apc.XXXXXX
(exactly 6 Xs).
To use POSIX-style shm_open/mmap put a .shm
somewhere in your mask. e.g. /apc.shm.XXXXXX
You can also set it to /dev/zero to use your
kernel's /dev/zero interface to anonymous mmap'ed
memory. Leaving it undefined will force an anonymous mmap.

On very busy servers whenever you start the server or
modify files you can create a race of many processes
all trying to cache the same file at the same time.
This option sets the percentage of processes that will
skip trying to cache an uncached file. Or think of it
as the probability of a single process to skip caching.
For example, setting apc.slam_defense
to 75 would mean that there is
a 75% chance that the process will not cache an uncached
file. So, the higher the setting the greater the defense
against cache slams. Setting this to 0
disables this feature.

When a file is modified on a live web server it really
ought to be done in an atomic manner. That is, written to a
temporary file and renamed (mv) the file into its
permanent position when it is ready. Many text editors,
cp, tar and
other such programs don't do this. This means that there
is a chance that a file is accessed (and cached) while it
is still being written to. This apc.file_update_protection
setting puts a delay on caching brand new files. The
default is 2 seconds, which means that if the modification
timestamp (mtime) on a file shows that it is less than 2
seconds old when it is accessed, it will not be cached.
The unfortunate person who accessed this half-written file
will still see weirdness, but at least it won't persist.
If all of the webserver's files are atomically updated, via
some method like rsync (which updates correctly),
this protection can be disabled by setting this directive to 0.
If the system is flooded with i/o and some update procedures
are taking longer than 2 seconds, this setting should be increased
to enable the protection on those slower update operations.

Mostly for testing and debugging. Setting this enables APC
for the CLI version of PHP. Under normal circumstances, it is
not ideal to create, populate and destroy the APC cache on every
CLI request, but for various test scenarios it is useful to be
able to enable APC for the CLI version of PHP easily.

Be careful changing this setting. This defaults to on, forcing APC to
stat (check) the script on each request to determine if it has been modified.
If it has been modified it will recompile and cache the new version.
If this setting is off, APC will not check, which usually means that to
force APC to recheck files, the web server will have to be restarted or the
cache will have to be manually cleared. Note that FastCGI web server configurations
may not clear the cache on restart. On a production server where the
script files rarely change, a significant performance boost can be
achieved by disabled stats.

For included/required files this option applies as well, but note that
for relative path includes (any path that doesn't start
with / on Unix) APC has to check in order to uniquely identify the file.
If you use absolute path includes APC can skip the stat and use that
absolute path as the unique identifier for the file.

On busy servers, when the web server is first started, or when many files
have been modified at the same time, APC may try to compile and cache the
same file multiple times. Write_lock guarantees that only one process
will attempt to compile and cache an uncached script. The other processes
attempting to use the script will run without using the opcode cache, rather
than locking and waiting for the cache to prime.

This feature is EXPERIMENTAL. The behaviour of this
directive, its name, and surrounding documentation may change without
notice in a future release of APC. This feature should be used at your
own risk.

RFC1867 File Upload Progress hook handler is only available if APC
was compiled against PHP 5.2.0 or later. When enabled, any file uploads
which includes a field called APC_UPLOAD_PROGRESS
before the file field in an upload form will cause APC to automatically
create an upload_key user cache entry where
key is the value of the
APC_UPLOAD_PROGRESS form entry.

Note that the hidden field specified by
APC_UPLOAD_PROGRESS must come before the file field,
otherwise the upload progress will not work correctly.

Note that the file upload tracking is not threadsafe at this point, so
new uploads that happen while a previous one is still going will disable
the tracking for the previous.

Note that the rate is only available once all file
transfers are completed.

The frequency that updates should be made to the user cache entry for
upload progress. This can take the form of a percentage of the total
file size or a size in bytes optionally suffixed with
"k", "m", or "g"
for kilobytes, megabytes, or gigabytes respectively (case insensitive).
A setting of 0 updates as often as possible, which may cause slower
uploads.

Enables APC handling of signals, such as SIGSEGV, that write
core files when signaled. When these signals are received,
APC will attempt to unmap the shared memory segment in order
to exclude it from the core file. This setting may improve
system stability when fatal signals are received and a large
APC shared memory segment is configured.

Avertizare

This feature is potentially dangerous. Unmapping the shared
memory segment in a fatal signal handler may cause undefined
behaviour if a fatal error occurs.

Notă:

Although some kernels may provide a facility to ignore various
types of shared memory when generating a core dump file, these
implementations may also ignore important shared memory segments
such as the Apache scoreboard.

I'm trying to get upload progress with apc_fetch.I founded apc_fetch always return false till the upload completed.After fews hours debug, I finally notice that my APC_UPLOAD_PROGRESS was set after the file form.

Want to avoid segmentation with apc.shm_segments?If your linux server limits the shared memory block size and you're forced to use apc.shm_segments instead, change the setting by using (here is 512M but change it as you like):
# sysctl -w kernel.shmmax=536870912

(but if you want the change to be permanent after a restart you would have to add the following line in /etc/sysctl.conf

kernel.shmmax=536870912)

and updating apc.ini

apc.shm_segments="1"
apc.shm_size="512"

apc.stat is an extremely important setting for a production server, especially if many files are accessed on every request, which is quite normal on complicated web applications.

Always aspire to use:
apc.stat="0"
so that APC does not try to check that each and every file exists on every request you make. It also means you can update files on your server without crashing incoming requests on that time fragment. Whenever you wish to force APC to re-read all the files, simply clear the cache or restart your server.

For anyone wondering why shm_segments is being ignored on their setup, it could be because of the following:

If you've configured APC to use memory mapped files (with the --enable-mmap option), the shm_segments setting is ignored unless you specify a file mask via the mmap_file_mask setting.

This is because APC won't attempt to create multiple anonymous files to map into memory without a mask (since it has no way of naming them sensibly). To set up multiple segments you have to give a file mask so they can be named separately.

apc.mmap_file_mask=/tmp/apc.XXXXXX

Make sure to use exactly 6 "X"s (this is the part that is changed by APC). You can place these files anywhere, they don't have to go in /tmp.

With that said, I'm not sure what the performance impact of having multiple MMAP segments would be. I'm guessing it would probably be negative so you probably don't want to do this.

If you are getting 0kb out of 0kb for your upload progress with large files, make sure that upload_max_filesize and post_max_size are larger than the file you are uploading. As far as I can tell, apc.max_file_size does not affect it.

apc_fetch always returned false. Turns out that "apc.rfc1867" was set to "0". I added this line to my php.ini:apc.rfc1867 = 1but it could have certainly been changed with ini_set(). That took me way to long to figure out.

Note: If you want to run a script on Windows with apc.enabled=1 as a scheduled task whilst another instance of php is running (like on a webserver) apparently you have to disable apc for this scheduled task, otherwise it will not run and you will have something in your error log like: PHP Fatal error: PHP Startup: apc_shm_create: shmget(0, 33554432, 658) failed: No such file or directory.

At the moment of writing the preload_path option is broken because of a bug in the APC source code which will not allow you to properly preload the cache.

The way to fix it :Inside 'main_apc.c' in the method called 'static int apc_load_data(const char *data_file TSRMLS_DC)', the length of the key of the value that needs to be stored is determined with the following line :key_len = strlen(key);If I am correct this is only the length of the string itself without the null-terminatorHowever, "_apc_store" seems to want the length of the key string including the terminator.If I change the line above to :key_len = strlen(key)+1;then the preload function works as expected.You can also notice that 1 character is missing when looking at the user cache entries apc.php. But if you try to use that as a key then APC will not return the contents so that didn't work as a workaround.

If one is able to compile the apc library from source, then one can of course easily fix this option by changing the source code.

Files in the specified path should have the extension '.data'.The filename itself will become the key for the data that is in that specific file.The data in the file is a serialized string representing what you want to assign to the specific key. For example s:2:"123" will generate the string "123".One can only specify 1 value for each key and it should be null-terminated.

It is not possible to preload PHP scripts.Only values that one retrieved with apc_fetch can be preloaded.

apc.include_once_override=1 can cause more problems than it solves. If you're running into weird errors regarding relative paths, make sure this setting is off. PHP 5.3 already implements most of the speed ups in these calls anyway.

apc.stat is an extremely important setting for a production server, especially if many files are accessed on every request, which is quite normal on complicated web applications.

Always aspire to use:apc.stat="0"so that APC does not try to check that each and every file exists on every request you make. It also means you can update files on your server without crashing incoming requests on that time fragment. Whenever you wish to force APC to re-read all the files, simply clear the cache or restart your server.